Chairlifts, gondolas, ski lifts and other cable driven conveyancing apparatus of the type conventionally employed in the skiing industry are subjected to loading and vibrational forces which are substantial. Such apparatus are typically constructed with a hanger arm having one end formed for connection to a drive cable and a second end which is connected to a frame or bail on which is mounted a chair, gondola, seat or the like. As used herein, the expression "chair frame" will be understood to include frame elements used to support chairs, seats, platforms, gondolas, and similar personnel and equipment carrying apparatus.
The coupling between the hanger arm and the chair frame is subjected to high stress forces and substantial vibration loads. A reoccurring problem in connection with such structures has been, therefore, that rigid couplings between the hanger arm and chair frame tend to fatigue. Additionally, even when metal fatigue does not produce failure of the coupling, the vibrations are undesirably transmitted to both the personnel being conveyed by the system and other components of the system.
One solution to this problem is simply to pivotally mount the chair or gondola frame to the hanger arm. Typical of this type of approach is U.S. Pat. No. 3,008,761. This solution eliminates fatiguing at the coupling through vibration, but it produces a new problem, namely, undesirable swinging of the chair. A similar pivotal mounting structure is shown in U.S. Pat. No. 3,134,342.
In U.S. Pat. No. 3,257,965 a ski lift hanger arm mount is shown in which the end of the hanger arm which is connected to the cable gripping device is pivotally mounted, with nylon washers providing frictional damping of the pivotal movement. Wear due to friction and the attendant need for adjustment and replacement of parts are disadvantages of this system. While perhaps acceptable for applications in which the skier retains his skis in contact with the ski slope, large swinging motion inherent in this type of mount is not advantageous when a skier is suspended above the ground.
U.S. Pat. No. 3,747,974 is an example of a chair frame and hanger arm mount which is relatively complex in structure and primarily concerned with the use of chairlift motion to open and close a protective housing.